Effect of powder dispersity on the optical properties of HIP sintered MgAl2O4 transparent ceramics

Abstract

Optical scattering centers in transparent magnesium aluminate spinel (MgAl2O4) ceramics substantially limit their applications in infrared domes or transparent windows. In this study, hot isostatic pressing (HIP) sintering was employed to fabricate high-quality transparent MgAl2O4 ceramics without the addition of sintering additive, and revealed that dispersion behavior of starting powders was crucial to the quality of MgAl2O4 ceramics. Microstructural evolution and optical quality of MgAl2O4 ceramics as the function of ball milling speed and pre-sintering temperature were systematically investigated. Despite increasing ball milling speed moderated powder agglomeration, large voids were still observed from the depth direction of the sintered ceramics. These voids could be further eliminated by employing PEI as the dispersant, and the in-line transmittance of the resulting ceramic was 86.5% at 800 nm, which was almost identical to the theoretical limit of MgAl2O4.